This invention relates to certain novel sulfur containing nitroaminobenzene dyes and to certain processes for synthesizing such dyes. More particularly it concerns dyes of this character in which the amino group is a secondary amino group. Furthermore, this invention also relates to dyeing processes for hair that employ such dyes and compositions for carrying out these hair dyeing processes. Dyes of the aforesaid character are of the direct dye type, not requiring any oxidizing agent for color development and are generally used in semi-permanent hair coloring compositions.
Direct dyes based on nitrobenzene derivatives have been known for a long time. These have generally taken the form of mono- or disubstituted nitrobenzenes wherein the substituent groups on the nitrobenzene are amino groups, substituted amino groups or hydroxy groups of which the O and N serve as electron donor groups (See Article by John F. Corbett in Vol. 5 Chapter VII of The Chemistry of Synthetic Dyes by K. Venkataraman, Academic Press, New York, 1971 (pp. 508-518). In these cases, the NO.sub.2 group of the nitrobenzene serves as the electron acceptor group. This system of donor and acceptor groups linked together by the unsaturated bridge that is provided by the benzene ring may serve to move the principal absorption band of the chromogen into the visible region.